#include <stdio.h>

int main()
{
    int i = 0;
    double sum = 0.0;
    int flag = 1;
    for (i = 1; i <= 100; i++)
    {
        sum += flag*1.0 / i;
        flag = -flag;
    }
    printf("%lf\n", sum);
    return 0;
}